The present invention relates to a permanent magnet starter, and particularly to a permanent magnet magnetic field type starter suitable for use in an automobile.
In a conventional starter, it has known during the starting of an engine when the collision force is reduced when a pinion gear of the starter meshes into a ring gear, for example as shown in Japanese patent laid-open No. Sho 57-168,057.
In this kind of the conventional starter, a pole core is moved toward the radial direction using the magnetic field which is generated by a magnetic field coil of a motor, and the rotation of a pinion clutch is restrained by such a force.
By effectively exhibiting the thrust force of the pinion clutch according to a helical spline, the pinon gear is meshed into the ring gear. After that, the return of the pinion gear due to the reaction force of the engine after the dash out of the pinion gear is prevented in accordance with a push rod which is positioned at a rear end of a clutch unit.
However, in the above stated conventional starter technique, since the magnetic field generated by the magnetic field coil of the motor is used as the rotation force of the pinion clutch, it is effective to a wound magnetic field type permanent magnet starter, however it can not apply in a field of a permanent magnet magnetic field type permanent magnet starter which has no magnetic field coil for exciting the motor.
Further, in the conventional starter techniques, since the pole core moves toward the radial direction, it is difficult to obtain a good shielding property surrounding the moving pole core. Further, taking into the consideration about the surrounding apparatuses it is necessary to arrange the components of the starter, thereby it presents a low service property.